Spray gun

ABSTRACT

A spray gun has a trigger actuated maneuvering pressure reduction valve therein. The maneuvering pressure upon depression of the trigger acts on a main pressure reduction valve thereby infinitely variably controlling the supply of compressed air to a compressed air operated ejector feeding spraying material to the spray gun.

United States Patent [151 3,674,209

Liedberg 1 July 4, 1972 [54] SPRAY GUN [56] References Cited [72] Inventor: Kurt Herman Liedberg, Skara, Sweden UNITED STATES PATENTS 73 Assigneez Atlas Copco Aktiebolag, Nacka Sweden 3,096,225 7/1963 Carr et al ..239/l43 X 3,385,522 5/1968 KOCk [22] Flled: Sept. 24, 1970 1,550,037 8/1925 McGarvey ..302/57 UX pp No: 74,970 1,755,329 4/1930 McCormack ..302/57 X Primary Examiner-M. Henson Wood, Jr. (30] Foreign Application Priority D t Assistant Examiner-Michael Y. Mar

AttorneyBauer and Goodman Oct. 6, 1969 Sweden ..13699/69 57 ABSTRACT [52] U.S.CI ..239/l43,222/l93,239/4l2,

239/4173 302/57 A spray gun has a trigger actuated maneuvering pressure 51 Int. Cl ..B05b 7/12 reducfim valve herein The mmuvering Press? [58] Field of Search ..239/15 142 143 412 417.3 depress the trigger acts Pressure valve thereby infinitely variably controlling the supply of compressed air to a compressed air operate-d ejector feeding spraying material to the spray gun.

8 Claims, 1 Drawing Figure SPRAY GUN This invention relates to spraying guns and more specifically to a spraying arrangement incorporating a hand sustained spray gun supplied with spraying material from a supply receptacle by the aid of a compressed air drivenejector to which compressed air is led from a main valve remotely controlled by a maneuvering means actuatable on the spray gun. Such spraying arrangements may find wide application for example in connection with the spraying of paint powder, plastic components, concrete, fiber cuttings, blasting means in powdery state, sand and steel blasting grit and other similar applications.

In hitherto presented designs, the delivery control of the spraying material is a problem particularly when it is desired to attain a wide and simultaneously preferably stepless variation of the quantity of the spraying material delivered. In spray guns it has thus been suggested to provide the spray gun with a pair of valve means operable in sequence one after the other by actuation of the gun trigger for purposes of adjusting the powder amount in two steps, but this solution becomes too expensive if it is tried to increase the number of valve steps for attaining increased fineness in the control.

The main objects of the invention are to provide, in a spraying arrangement of the above mentioned type, an effective infinitely variable control of the spraying material supply within wide limits of variation and by simple aids in respect of design.

SUMMARY OF THE INVENTION For the above and other purposes there is accordingto the invention provided a spraying arrangement comprising a hand sustained spray gun, a spraying material supply hose connected to said spray gun, a supply receptacle separate from said spray gun for providing a source of spraying material, supplying means for compressed air, a compressed air driven ejector associated with said receptacle and connected to said supply hose for carrying away spraying material from said receptacle on into said hose and to said spray gun, a main pressure reduction valve connected to said compressed air supplying means and to said ejector at said supply receptacle for controlling operation of the latter, and a rnanoeuvering pressure reduction valve on said spray gun connected to said compressed air supplying means and to said main pressure reduction valve for infinitely variable control of the latter remotely from said spray gun.

The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which one embodiment of the invention is illustrated by way of example. It should be understood that this embodiment is only illustrative of the invention and that various modifications thereof may be made within the scope of the appended claims.

In the drawing, the FIGURE illustrates the invention as applied by way of example to a spraying arrangement incorporating a spray gun for spraying paint powder and electrostatically charging the powder particles thus sprayed.

The spray gun l intended for electrostatic charging of particles is by means of a high tension cable 9 connected to a high tension source, not shown. Spraying material such as a mixture of paint powder and air is supplied via a hose 16 from a supply receptacle 19. The powder in the receptacle 19 is fed downward to a ring groove 23 in an ejector 24 in which the powder-air mixture is formed by compressed air rushing in from an ejector tube 20, the air transporting the powder via the hose 16 to the spray gun 10. The ejector tube is supplied with compressed air from a source of compressed air, not shown, via a conduit 22 and a main pressure reduction valve 18.

The main valve 18 comprises a housing and a valve body 25 coacting with a seat 26 in the housing and being mounted to open against the direction of fluid flow of the compressed air arriving from the conduit 22. The valve body 25 is normally urged onto the seat 26 by a helical closing spring 27. The main valve 18 operates as a pressure reduction valve and therefore the valve body 25 thereof is aflixed to a piston means or a diaphragm 21 which within the main valve housing defines by way of partitioning on the one hand a main chamber 28 between the seat 26 and the ejector tube 20 and on the other a balancing chamber 29 for adjustment of the degree of pressure reduction in the main valve 18 by aid of compressed air. The balancing chamber 29 is in communication with the surrounding atmosphere by way of a fine pressure equalization opening 30. i

A trigger 14 is movably or pivotally journalled about a pivot 11 at the rear end of the spray gun, l0 and carries a fixed arm 12. The arm 12 cooperates with a maneuvering pressure reduction valve 31 in the rear end of the spray gun 10 which is supplied with compressed air from a suitable source of compressed air via a conduit 15. The maneuvering pressure reduction valve 31 comprises a valve body 8 which by a helical clos ing spring 7 normally is urged onto a seat 32. The valve body 8 is mounted to open against the direction of fluid flow of the compressed air supplied thereto via the conduit 15. Furthermore the maneuvering pressure reduction valve 31 comprises a valve lifting piston 33 which is slidablly but sealingly guided in a guide passage 34 in the spray gun downstream of the valve body 8. Between the arm 12 of the trigger 14 and the valve lifting piston 33 is inserted an adjusting spring 6. The valve lifting piston 33 bears by a valve lifting finger 13 against the valve body 8 throughthe opening of the seat 32. The guide passage 34 is by means of a conduit 17 connected to the balancing chamber 29 of the main valve 18.

In the inactivated state of the trigger the valve body 8 of the maneuvering pressure reduction valve 31 is kept closed on the seat 32 by the helical spring 7, the balancing chamber 29 of the main valve 18 is relieved via the pressure equalizing opening 30 and the valve body 25 afiixed to the diaphragm 21 sits on its seat 26 under the compressive force of the helical closing spring 27. There is thus performedl no material supply to the spray gun 10.

When the trigger 14 is depressed, a switch, not shown, is caused to apply in a manner well known in the art by way of the cable 9 high tensionto the electrodes, not shown, of the spray gun 10. Simultaneously therewith the adjusting spring 6 is compressed in proportion to the depression of the trigger 14. As a result the valve body 8 actuated by the valvelifting finger 13 is caused to deliver compressed air from the conduit 15 at reduced pressure on to the conduit 17 and the balancing chamber 29 such as to increase the pressure level therein proportionally to the depression of the adjusting spring 6. With increased pressure in the balancing chamber 29 the reduction valve body 25 is caused to deliver compressed air at gradually increased pressure level to the main chamber 28 and the ejector tube 20. The compressed air entering the ejector carries away powder therewith via the ring groove 23 by an amount increasing with increased air pressure on into the conduit 16 and thence to the spray gun 10 past the electrodes thereof for purposes of charging the powder particles and thence out towards the work piece which is to be coated by paint powder. Through the movements of the trigger there is attained an infinitely variable effective control of the delivered amount of powder proportionally to the depression of the trigger 14 through which is controlled the amount of transporting air working in the ejector 24.

In other applications wherein electrostatic charging would be undesirable, the above mentioned high tension equipment and details will be omitted and the spray gun is then designed for conventional ejector supported spraying. If needed the spraying can be further assisted by conventional auxiliary pneumatic spray nozzles at the tip of the gun.

What is claimed is:

1. A spraying arrangement comprising:

a hand sustained spray gun;

hose means for supplying spraying material to said spray gun;

a supply receptacle separate from said spray gun for providing a source of spraying material;

supplying means for compressed air;

a compressed air driven ejector associated with said receptacle and connected to said supply hose means for carrying away spraying material from said receptacle on into said supply hose means and to said spray gun;

a main pressure reduction valve coupling said compressed air supplying means to said ejector for controlling operation of said ejector;

a spring loaded pressure reduction valve on said hand sustained spray gun connected to said compressed air supplying means and to said main pressure reduction valve for infinitely variably controlling of said main pressure reduction valve remotely from said spray gun; and

operating means on said hand sustained spray gun for varying the loading of said spring in said spring loaded pressure reduction valve.

2. A spraying arrangement according to claim 1 wherein said operating means includes a trigger movably joumalled on said spray gun and coupled to said spring of said spring loaded pressure reduction valve for varying the loading thereof.

3. A spraying arrangement according to claim 2 wherein said main pressure reduction valve includes a housing, a main valve body mounted in said housing to open against the direction of fluid flow of the compressed air supplied to said ejector, and a pressure balancing means in said housing downstream of and operatively connected to said main valve body for balancing the pressure after said main valve body by air pressure defined by said spring loaded pressure reduction valve.

4. A spraying arrangement according to claim 3 wherein said pressure balancing means is a diaphragm affixed to said main valve body and partitioning said housing into a main chamber between said main valve body and said ejector, and a balancing chamber connected to said spring loaded pressure reduction valve.

5. A spraying arrangement according to claim 2 wherein said spring loaded pressure reduction valve includes a gun valve body mounted in said spray gun against the direction of fluid flow of the compressed air supplied to said spray gun, said spring of said spring loaded pressure reduction valve being mounted in said spray gun between said trigger and said gun valve body to urge the latter adjustably against the direction of fluid flow.

6. A spraying arrangement according to claim 5 wherein said spring loaded pressure reduction valve includes a valve lifting piston means coupled to said gun valve body, said valve lifting piston means being slidably but sealingly mounted in said spray gun downstream of said gun valve body and in engagement therewith, said spring of said spring loaded pressure reduction valve being mounted between said trigger and said valve lifting piston means.

7. A spraying arrangement according to claim 6, wherein said trigger includes an arm bearing against said spring of said spring loaded pressure reduction valve, said trigger being pivotally joumalled on said hand sustained spray gun.

8. A spraying arrangement according to claim 5 including second spring means urging said gun valve body in the direction of fluid flow of the compressed air supplied to said spray gun to maintain said valve normally closed. 

1. A spraying arrangement comprising: a hand sustained spray gun; hose means for supplying spraying material to said spray gun; a supply receptacle separate from said spray gun for providing a source of spraying material; supplying means for compressed air; a compressed air driven ejector associated with said receptacle and connected to said supply hose means for carrying away spraying material from said receptacle on into said supply hose means and to said spray gun; a main pressure reduction valve coupling said compressed air supplying means to said ejector for controlling operation of said ejector; a spring loaded pressure reduction valve on said hand sustained spray gun connected to said compressed air supplying means and to said main pressure reduction valve for infinitely variably controlling of said main pressure reduction valve remotely from said spray gun; and operating means on said hand sustained spray gun for varying the loading of said spring in said spring loaded pressure reduction valve.
 2. A spraying arrangement according to claim 1 wherein said operating means includes a trigger movably journalled on said spray gun and coupled to said spring of said spring loaded pressure reduction valve for varying the loading thereof.
 3. A spraying arrangement according to claim 2 wherein said main pressure reduction valve includes a housing, a main valve body mounted in said housing to open against the direction of fluid flow of the compressed air supplied to said ejector, and a pressure balancing means in said housing downstream of and operatively connected to said main valve body for balancing the pressure after said main valve body by air pressure defined by said spring loaded pressure reduction valve.
 4. A spraying arrangement according to claim 3 wherein said pressure balancing means is a diaphragm affixed to said main valve body and partitioning said housing into a main chamber between said main valve body and said ejector, and a balancing chamber connected to said spring loaded pressure reduction valve.
 5. A spraying arrangement according to claim 2 wherein said spring loaded pressure reduction valve includes a gun valve body mounted in said spray gun against the direction of fluid flow of the compressed air supplied to said spray gun, said spring of said spring loaded pressure reduction valve being mounted in said spray gun between said trigger and said gun valve body to urge the latter adjustably against the direction of fluid flow.
 6. A spraying arrangement according to claim 5 wherein said spring loaded pressure reduction valve includes a valve lifting piston means coupled to said gun valve body, said valve lifting piston means being slidably but sealingly mounted in said spray gun downstream of said gun valve body and in engagement therewith, said spring of said spring loaded pressure reduction valve being mounted between said trigger and said valve lifting piston means.
 7. A spraying arrangement according to claim 6, wherein said trigger includes an arm bearing against said spring of said spring loaded pressure reduction valve, said trigger being pivotally journalled On said hand sustained spray gun.
 8. A spraying arrangement according to claim 5 including second spring means urging said gun valve body in the direction of fluid flow of the compressed air supplied to said spray gun to maintain said valve normally closed. 